Study: Teens' Minds Wired for Cheap Thrills

— Adolescents who experiment with drugs and alcohol couldn't pick a worse time in their lives to do it.

At that stage in their mental development, the part of the brain that tells them to experiment with drugs is much farther advanced than the part that's supposed to lend a little judgment to the situation.

If they keep going down that path, they may enter their 20s addicted to drugs, partly because addiction may owe as much to the mental developmental agenda as it does to substance abuse.

Doing drugs during the teenage years "really does make concrete changes in the way your brain operates, in a permanent sense," says Andrew Chambers, a Yale University psychiatrist and lead author of a study in the June issue of the American Journal of Psychiatry.

Chambers and his associates at Yale examined 140 previously completed research projects to see if they could link the various stages of development that adolescents go through with the high rate of addictions that occur early in life.

Earlier Start, Harder to Quit

Most people who can't give up drugs or alcohol or smoking were already addicted in their teenage years, the researchers found. That addiction was due to various causes. Some adolescents have a predisposition toward impulsiveness or recklessness because of genetics or a social situation, making them particularly vulnerable to addiction.

But the researchers also found reason to believe that teenage addiction is partly caused by different rates of development by different parts of the brain. As kids, we look for cheap thrills and exciting adventures, because that's what kids do, and the part of the brain that stimulates that behavior develops very early and rapidly. When we grow up, we're supposed to put away childish things and make mature decisions, but the part of the brain that allows us to do that develops much more slowly.

And that, the researchers conclude, is one reason adolescents and teenagers are more vulnerable to various addictions than any other age group.

The numbers speak for themselves.

"Over 40 percent of adult alcoholics experience alcoholism-related symptoms between ages 15 and 19, and 80 percent of all cases of alcoholism begin before age 30," the researchers report in their paper. "The median reported age of initiation of illicit drug use in adults with substance use disorders is 16 years, with 50 percent of cases beginning between ages 15 and 18 and rare initiation after age 20."

The list goes on. Most adult smokers began before the age of 18. And the earlier the kids get into drugs, the stronger the addiction, and the greater the morbidity.

Teen Brain Says ‘Go’

Why people use these dangerous substances, and why we sometimes become addicted, is a very complex mosaic of human development, social pressures, genetics and other factors that produce a very incomplete picture. As Chambers himself notes, not everybody who does drugs or drinks booze as an adolescent goes down the tubes. Some people outgrow it, so whatever brain damaged occurred early on, if any, didn't leave them permanently crippled.

"A lot of people do use a lot of drugs or alcohol when they are in their late teens and early 20s and come out OK," he says. As a college professor, he knows not all those students are spending all their time buried in books.

"Man, there's a lot of partying that most people go through in college," he says, "and most of those people make it out of that and settle down into non substance disordered patterns."

But a lot of them don't, and the reasons are not yet clear.

The researchers focused on the release of dopamine in the brain, which operates "like a general 'go' signal," they report. Drugs, sex, even video games release dopamine, stimulating the brain and making us want more. But lots of other things also generate dopamine.

Food and even stress and trauma also release dopamine, and that has set researchers off in a new direction. Dopamine isn't just released by rewarding things. It's also released by events or circumstances that may threaten our survival or way of life.

Inhibition Comes Too Little Too Late

So it isn't all about "reward and pleasure," Chambers says. Since dopamine is released by a wide variety of stimuli, there must be some common ground between such things as drugs, food, sex and stress. That common denominator, many scientists believe today, is motivation.

Motivation can either pull us back from dangerous substances, like addictive drugs, if our "mature" side of mental development is on the job, or it can push us farther into harm's way, if the kid is still in charge.

Getting high, or taking a risk, is an early motivation among adolescents who are eager to try out their walking shoes. But a little later, motivation should shift somewhat as the part of the brain that inhibits impulses matures.

But by that time, addiction may have already set in.

It's not easy being a kid.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.